Who is Afraid of Vaccine Hesitancy?

In a recent philosophical discussion of Molière’s 1673 comedy The Imaginary Invalid, Elanor Taylor revisits one of the most durable jokes in the history of scientific explanation. During a mock medical examination, a candidate is asked why opium makes people sleep. He explains that opium possesses a virtus dormitiva, a “dormitive virtue”, whose nature is to induce sleep. The physicians enthusiastically approve his answer and welcome him to the learned profession of medicine. As Taylor notes, the expression has endured for centuries as an exemplar of explanatory failure — circular reasoning, vacuous tautology — even if philosophers continue to disagree about precisely why it fails [1].

The joke is easy to understand. Why does opium cause sleep? Because it has the property of causing sleep. Dress the answer in Latin, place it in the mouth of an expert, and what is essentially a restatement of the observation suddenly acquires intellectual gravitas. I would like to suggest that contemporary public health has developed its own virtus dormitiva: vaccine hesitancy. Why do some people delay or decline vaccination despite availability? Because they are vaccine hesitant. How do we know that they are vaccine hesitant? Because they delay or decline vaccination despite availability.

Of course, much like opium does put people to sleep, people sometimes do hesitate about getting vaccinated despite availability, as they hesitate about going along with many other medical interventions — or with any course of action, for that matter. They question, postpone, accept some courses of action and decline others, change their minds, or refuse altogether. There is nothing imaginary about these behaviours. Yet to my knowledge, few such forms of reluctance have acquired anything resembling the institutional life of “vaccine hesitancy”: an official indexing term, dedicated models and scales, research programs, expert reports, educational campaigns, and policy strategies.

In fairness, as Taylor notes, dispositional explanations are not necessarily meaningless: a disposition may sometimes point us toward something that genuinely explains an outcome. My cat, for example, invariably looks for the highest available perch. Calling him a climber may have some explanatory value because it describes a broader disposition I can observe in many settings. Saying that he is on top of my kitchen cabinets because he has a virtus climbitiva, however, merely gives his climbing a Latin-sounding name. Put another way, the question is whether a label actually supplies explanatory information or merely renames the very phenomenon we began by asking about.

Applied to vaccination, this distinction matters. If “vaccine hesitancy” is simply shorthand for a person being uncertain about or unwilling to receive a vaccine, little follows. But once hesitancy is treated as an underlying “condition” that explains an observation — and not just any condition, but a form of cognitive, attitudinal, behavioural, political, or even moral deviance, sometimes shading into the more openly stigmatizing label “antivaxxer” — an entire research program with remarkable potential for social control becomes possible. Who is hesitant? What demographic groups are most or least hesitant? What psychological characteristics predict hesitancy? Does hesitancy arise from insufficient knowledge, distrust of authority, political ideology, social-media exposure, susceptibility to “misinformation”, or failure to appreciate the “scientific consensus”? Which messages might reduce it? Who should deliver those messages? How can “vaccine confidence” be restored? And eventually: what should be done when persuasion fails? At that point, a descriptive category has become an object of governance.

Why Vaccines?

There is something peculiar about this vocabulary that becomes more obvious if we try to apply it elsewhere in medicine. Suppose a patient reads the evidence, for instance, the package insert of a medication, and decides against taking it. We might disagree with the decision. We might think the patient misunderstood the evidence. We might recommend reconsideration. But we would rarely build a research program or policy initiative around the patient’s “statin hesitancy”, “chemotherapy hesitancy”, or “antidepressant hesitancy”. Why, then, has reluctance toward vaccination acquired such distinctive scientific, institutional, and even moral weight?

The question matters because vaccines are medical interventions. Whether any particular vaccine is appropriate for any particular person is, or should be, an empirical and clinical question involving expected benefits, possible harms, alternatives, individual circumstances, and the quality of the available evidence. Yet “vaccine hesitancy” can subtly reverse that relationship. Instead of the intervention, or those promoting it, being required to justify it to the person, the person is required to explain why she “hesitates”, or even why she is not “willing” to “embrace” vaccination [2].

That reversal became especially visible at the height of the Covid event, when vaccination was often required for access to public spaces, transportation, and major social institutions, including education and healthcare. Specifically, my research on healthcare workers under Covid vaccination mandates across three Canadian provinces, Ontario, British Columbia, and Alberta, indicated that workers who questioned or declined vaccination were framed by leading institutions and social actors as “hesitant”, insufficiently trusting, misinformed, ideologically motivated, or otherwise deficient [3–5]. In other words, they became the analytic object, while the evidentiary, legal, and policy premises underlying the mandates received comparatively little scrutiny.

A similar pattern was also visible in Canadian litigation, where courts frequently accepted official public-health claims through “judicial notice”, defined by the Supreme Court of Canada as a rule that “dispenses with the need for proof of facts that are clearly uncontroversial or beyond reasonable dispute”. Facts judicially noticed, the Court continued, “are not proved by evidence under oath. Nor are they tested by cross-examination”. The threshold is therefore strict: such facts must be either “so notorious or generally accepted as not to be the subject of debate among reasonable persons” or capable of “immediate and accurate demonstration” from sources of “indisputable accuracy” [6]. In other words, the rule is meant for claims whose factual status is closer to “the earth is not flat” than to empirical claims whose validity depends on evidentiary adjudication. Meanwhile, healthcare institutions largely reframed workers’ concerns about coercive practices, suppression of professional judgment, violations of ethical principles, and the contested evidence supporting vaccine safety and efficacy as “vaccine hesitancy”. Yet calling the concerns reported by most respondents among the more than 700 healthcare workers surveyed by me and my team “hesitancy” says essentially nothing about whether those concerns were warranted scientifically, legally, ethically, or otherwise.

From Explanation to Governance

It is with this reframing that the concept of ‘vaccine hesitancy’ becomes interesting and politically powerful [5,7]. Once it is constituted as a public health “problem”, its causes can be studied, its prevalence can be measured, populations can be stratified according to their presumed degree of hesitancy, communication campaigns can be designed to reduce it, “trusted messengers” can be enlisted to overcome it, and behavioural interventions can be deployed to change it. What disappears remarkably easily is the antecedent question: were there any good reasons to hesitate? And that question cannot be answered by launching research programs, global health policy “initiatives”, or media campaigns against “hesitancy”. Whether hesitation is reasonable depends not simply on the person’s disposition, but on the intervention being questioned: what is known about its benefits and harms, how certain that knowledge is, what alternatives exist, who is being asked to accept it, and under what conditions.

In 2019, the World Health Organization famously — or infamously — included “vaccine hesitancy” among its top ten threats to global health, alongside threats such as air pollution and “fragile and vulnerable settings”, the latter encompassing drought, famine, conflict, and population displacement [8]. In my research on the Covid policy response at multiple levels — individual, institutional, epistemic [9–18] — I have documented how consequential this framing is. Specifically, locating the “problem” primarily in people’s attitudes, emotions, knowledge, degrees of trust, or susceptibility to “misinformation” diverts attention away from the evidentiary, ethical, institutional, and coercive dimensions of the vaccination policy itself — a form of power long examined by scholars of medicalization and political language: the capacity of ostensibly scientific health categories to organize public understanding, shape the narrative, and legitimize some courses of action while delegitimizing others [19–21].

Interestingly, none of this requires attributing sinister intentions to any particular person or institution. As Robert Merton observed, the subjective intentions of social actors can be distinguished from the objective consequences of their actions. The relevant question is therefore not what policymakers or researchers privately intend, but what the category of vaccine hesitancy actually does once embedded in research, policy, and institutional practice [22]. Applied to Covid policy, one need not speculate about policymakers’ intentions to observe and assess the effects of organizational discourses and practices in the larger social order. And with Covid vaccination, especially when mandatory, these effects have been problematic, to put it mildly. As my collaborators and I have documented among healthcare workers, they have included substantial physical, mental, emotional, and social harms — reported vaccine harms, workplace conflict, strains on health services, moral injury, broken relationships, family distress, loss of livelihood, and more [4,11–16].

Perhaps public-health officials and “vaccine hesitancy” researchers sincerely believe that they are protecting people. Perhaps some among them understand the political work performed by the label “vaccine hesitant”. Perhaps financial, professional, institutional, or ideological interests shape the field in ways participants themselves only partly perceive. These are empirical questions, perhaps worth asking. But we do not need to answer them to examine what ideological and material work the category “vaccine hesitancy” actually performs. And what it does is consequential: it converts a decision concerning a medical intervention into an attribute of the person making the decision. Once that transformation has occurred, the intervention itself recedes from scrutiny, and increasingly sophisticated explanations are developed for why some people fail to accept vaccines, Covid or other. Simultaneously, measures that might once have appeared extreme, unacceptable, or even unimaginable become normalized as “common sense”, and what began as exceptional becomes simply “the way things are”, and perhaps ought to be.

The ‘Virtus Hesitativa’?

Molière’s joke becomes less funny when a functional equivalent of the virtus dormitiva — let us call it a “virtus hesitativa” — begins governing people’s lives. The aspiring physician merely received professional approval for appearing to explain why opium induces sleep. Vaccine hesitancy has acquired far more formidable institutional backing. Indeed, while to my knowledge the “virtus dormitiva” did not make it too far in the halls of medical fame, “vaccine hesitancy” certainly did. Upon its official inclusion in the medical lexicon in 2022, one can now systematically search the National Library of Medicine for information about it [23], much like one can systematically search the literature on diabetes, multiple sclerosis, or cancer.

“Vaccine hesitancy” also frequently appears in peer-reviewed journals, public-health strategies, behavioural research, calls for grant applications, government communications, and the pronouncements of major international health institutions. It comes equipped with models, scales, predictors, determinants, interventions, experts, and conferences [24–30]. All of this produces an extraordinary appearance of explanatory depth. Yet strip away the apparatus and the original observation remains: some people do not want a vaccine despite availability. Nope. Not even when “acceptance” may have come with a free ride to college [31] or a luxury cruise [32], as it did at the outset of the global vaccination campaign. And, as it seems, whatever the initial enthusiasm, it has not exactly endured. Certainly not in Canada, where booster uptake has nosedived despite continued promotion by public health authorities [33].

A similar challenge appears to surround calls for “vaccine equity” in Africa, where low uptake is routinely framed as a problem of inequitable access, even as studies document people’s concerns about vaccine harms, pharmaceutical-industry interests, and lack of government transparency [34,35]. In other words, what is treated as insufficient access may instead reflect the fact that people simply do not want vaccines, and therefore “hesitate” about “embracing” them. This has prompted increasingly elaborate forms of “social listening” and “community engagement”, apparently to understand what people think so that, in the WHO’s own words, “targeted strategies” can be designed to “generate and sustain demand” [36]. Clearly, dealing with “vaccine hesitancy” has proved more difficult than measuring it. But I digress.

At any rate, the intellectually interesting questions begin, rather than end, when we question the concept. What evidence supports accepting a given vaccine? Or declining it? What adverse events have been observed after receiving that vaccine? What are the dangers of not taking it? What alternatives are available, and what risk is vaccination claimed to protect against? And most fundamentally, why should disagreement with a recommendation be presumed to constitute a “problem” requiring correction? This is where Edward Albee comes to mind. Who’s Afraid of Virginia Woolf? has often been read as a play about truth and illusion, and about what remains when sustaining illusions are stripped away [37]. I am, therefore, tempted to ask the analogous question about “vaccine hesitancy”: Who’s Afraid of “Vaccine Hesitancy”? I suspect that the institutions and social actors that confidently deploy the term today have the most to lose if the concept fades from public attention, because once the “virtus hesitativa” loses its scientific gravitas, the elaborate architecture built to identify, explain, measure, and correct the “hesitant” subject confronts a considerably more demanding problem, and arguably the real one: it is then compelled to offer good reasons and solid evidence to justify vaccination.

If I may be forgiven for speculating, perhaps these institutions and social actors are afraid that “vaccine hesitancy” may someday suffer the fate of other once-authoritative categories whose scientific standing later collapsed, although not before generating substantial bodies of “knowledge” in peer-reviewed medical journals. Examples include hysteria, which encompassed a range of behaviours and emotions attributed disproportionately to women constrained within male-dominated societies [38]; drapetomania, the supposed “tendency” of enslaved people to run away that preoccupied 19th-century psychiatry [39]; and, more recently, homosexuality, removed by the American Psychiatric Association from the Diagnostic and Statistical Manual of Mental Disorders in 1973 [40], with the World Health Organization following up in 1990 —close to 20 years later [41]. All of these remind us that institutional recognition does not guarantee a concept’s scientific shelf life.

Karl Popper might have found the irony difficult to resist. A category presented as scientific should ultimately be judged by whether it withstands critical scrutiny and explains anything of substance, not, as some expert guidance has implied, by the reputation, brand, or perceived credibility of the institutions promoting it [42]. Perhaps that is what is really frightening. Will “vaccine hesitancy” someday lose even its appearance of explanatory power? Who, then, will be afraid of a world without “vaccine hesitancy”?

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